31 Evaporative Purge Flow Monitor Failure - (P 0441)

31 EVAPORATIVE PURGE FLOW MONITOR FAILURE - (P 0441)

There are two different tests for the evaporative purge flow monitor. The first test determines how much corruption takes place in the long term memory cells due to an evaporative canister that has absorbed fuel vapors. (Refer to Fuel System Monitor for information involved with long term memory.) Purge free cells include cells 2 and 5 for all vehicles, cell 12 for vehicles with an automatic transmission, and cell 13 for vehicles with a manual transmission. The Powertrain Control Module (PCM) de-energizes the Duty Cycle Purge (DCP) solenoid, which blocks the flow of vapors from the evaporative canister to the intake manifold. The amount of injection pulse width correction is then recorded in these memory cells. The PCM recognizes that the DCP solenoid and the evaporative canister are functional if there is a 5% shift in injection pulse width correction from the purge free cells to the purge normal cell.

The second test takes place only if the first does not pass. To enable this portion of the monitor, the following conditions must be met:

- Barometric pressure must be greater than 25.6 in. of mercury
- Engine RPM less than 2048
- Manifold Absolute Pressure (MAP) sensor voltage between 1.38 volts and 2.0 volts
(The previous two parameters indicate that the PCM is monitoring in long term cell 2)
- Vehicle speed between 28 - 48 MPH
- Based on Throttle Position Sensor (TPS), MAP, RPM, battery voltage, and generator duty cycle, the engine must maintain a steady operation
- To run the test, these conditions must be held for at least one minute

The PCM de-energizes the DCP solenoid. For the next one-half second, the PCM waits for the MAP to stabilize, then for the next two seconds it averages the MAP voltage. The PCM then energizes the DCP solenoid. For the next one half second, the PCM waits for the MAP to stabilize, then for the next two seconds it averages the MAP voltage. If the PCM fails to recognize a shift in MAP voltage under the previous conditions, one failed count is recorded in the PCM's memory. To fail a trip, the PCM must recognize six failed counts. If one of the test pass, the testing is done. The PCM requires that it fails two trips to illuminate the MIL and record a DTC.

PENDING
The evaporative purge flow test does not run if the MIL is illuminated due to:

- Misfire fault
- O2 monitor fault
- Fuel system rich fault
- Fuel system lean fault
- EGR monitor fault
- MAP fault
- TPS fault
- Engine Coolant Temperature (ECT) fault
- DCP solenoid electrical fault

CONFLICT
The monitor does not run if any of the following are present:

- Catalyst test is in progress
- EGR monitor test in progress, or a one trip EGR monitor fault
- Fuel system rich test in progress, or a one trip fuel system rich fault
- Misfire test is in progress, or a one trip misfire fault
- one trip fuel system lean fault
- one trip O2 monitor fault

The Evaporative Purge Flow monitor malfunction could possibly be caused by problems with any of the following components:

- Hose from the throttle body to the DCP Solenoid (leaking or plugged)
- DCP solenoid
- Hose from the DCP solenoid to the evaporative canister (plugged) Evaporative canister (plugged)